New Keyboards not recognized by either PC

I have 2x 32Bit PCs x XP. Have two newly bought keyboards 1 x microsoft & 1x logitech basic cord keyboards. Neither keyboard on either machine are detected by the PCs. Current keyboards are still working.

I've tried sw/off- plug in KB- sw/on, AND Sw off/sw on & then plug in KB. Both methods no response. These are basic cord keyboards no software supplied nor there should be.

Apart from gremlins, what's going on & what do I do to activate them? They both cannot be faulty. I'm sure if I take them back to the shop he'll plug 'em in & they'll work.